Method of assembling a limp diaphragm actuator



Aug. 9, 1960 J. F. ENGELBERGER 2,948,060

METHOD OF ASSEMBLING A LIMP DIAPHRAGM ACTUATOR Original Filed May 6,1955 INV TOR. 10% II M KM...- W, K 12g United States PatentO METHOD OFASSEMBLlNG A LIMP DIAPHRAGM ACTUATOR Joseph F. Engelberger, Monroe,.'Conn., assignor to Manning, Maxwell 8: Moore, Inc., Stratford, Conn.,a corporation of New Jersey .Qriginal application May 6, 1955, Ser. No;506,488,

now Patent No. 2,839,086, dated June 17, 1958. Di-

vided and this application Oct. 18, 1957, Ser. No. 690,921

. '4 Claims. (Cl. 29-454) The present invention relates to pressureresponsive actuators, and, more particularly, to pressure responsiveactuators of the diaphragm type wherein changes in pressure of ameasured variable are converted intocorresponding motion of an outputshaft. 'While the invention isof general application in the diaphragmactuator field it has particular utility in high temperatureapplications such as those encountered in aircraft; turbine coninconnection with a gas turbine control system wherein there is provided apressure ratio type actuator which may be used at high temperatures andwhereinthe spring rate normally encountered in pressure responsiveactuators of this type is substantially eliminated. Specifically, thepresent invention is a division of my copending application, SerialNumber 506,488, filed May 6, 1955, now 5. Patent No. 2,839,086, which isassigned tothe same tassignee as the present invention.

: .In the pressureresponsive actuator. iield prior art arrangementshave. heretofore proposed the use of a piston andv cylinder-arrangementwherein around diaphragm, Q tusually of .rubber or .woven .fibres bondedtogether, is it clamped at the periphery thereof to the cylinder walland r is securedtothe piston headso that variations inpressure you thediaphragm produce movementof the piston shaft. In. these round diaphragmarrangements the effective, diaphragm. area may be varied by slopingthe:cylinder walls i and piston head sothat as'ithe'pist'on is moved thedia- ;phragm issupported ratt varying diameters .andhence has a variableeffective area.

While such prior art arrangements are suitable for their of hot gasesorother contaminants in the surrounding .rnedium. Furthermore, a metaldiaphragm cannot be .used. in these priornart limpdiaphragm arrangementssince thediaphragm-mustqstretch in onerdirection as the it piston moves.

While other prior art arrangements ,have N employed a metal diaphragm,they are unsatisfactory for pressure ratiocontrol applications due tothe fact that these metal diaphragmswere stressed in proportion to theoutput movement and have an inherent spring rate which produces avariation in thepressure ratio measurement in accordance with changes intheabsolute pressure level at which theratio is taken. Furthermore,these stressed diaphragm arrangements, have such, a-small total outputmovement that they are entirelyunsuitable for control systemapplications wherein a ,relativelylong actuator stroke is required.

It,is, therefore, an .object of the present, invention to provide a new,and improved limp diaphragm actuator It is another object of thepresentinvention to' pro- Q trol systems. i The invention, therefore, will bedescribed ice vide a new and improved pressure responsiveactuatorwherein a limp metal diaphragm may beemployed as the pressure responsiveelement.

It is a further object of the invention to provide a new and improvedlimp diaphragm actuator which may be employed at high temperatures toprovide accurate pressure measurement.

It is a still furtherobject of the present invention to provide a newand improved limp metal diaphragm actuator wherein the diaphragm hassubstantially no spring rate.

Another object of the present invention resides in the provision of anew and improved pressure ratio responsive diaphragm actuator which maybe used at high temperatures and is substantially insensitive tovariations in the absolute pressure level.

A further object of the present invention resides in the provision of alimp metal diaphragm actuator where in the diaphragm is not stretched ordistorted throughout the full stroke of the actuator.

A still further object of the present invention resides in the provisionof a new and improved method of male inga limp diaphragm actuatorwherein extremely close tolerances are provided between the movableedges of the diaphragm and the actuator body to minimize leakagetherebetween.

Briefly, in accordance with one aspect of theinvention, a rectangulardiaphragm actuator is provided wherein the diaphragm is supported on thebodyof the actuator only on two opposed sides thereof, a movable pistonsupporting the intermediate portion 'of 'r the diaphragm. The.diaphragm: is made. of relatively thin, flexible metal and theunsupported edge portionsof the: diaphragm are in contiguity with the.endplates of the actuator body to provide. an effective seal, this sealbeing obtained in accordance with themethod ofthe present in-- ventionby finishing the ends'of the diaphragm;the actuator body and the endplates to a highdegree of-ilab ness so that leakage around'theunsupported'endrportions' of the diaphragm is minimized. Withthisarrangement the. diaphragm is' not stretched at anypOint during theentire; stroke of the actuator, but instead forms true catenariesbetween the supporting edges of the actuator body and piston so that thediaphragm assumes the ideal shape to keep stresses thereon to aFurthermore, the actuator has substantiallyno spring rate since themetal diaphragm is fiexed only in two dimensions and itmovement' ofthepiston does not produce any appreciable change in stress on thediaphragm. 'Eventhough the would be constant-throughout the stroke ofthe actuator and the only effect thereof would be to introduce a deadband in the controlling action of the actuator. "In accordance with afurther aspect of the invention, aypressure i of these diaphragmsvarying with actuator movement so ,that a linear' stroke actuatorisprovided which has a lowing specification takenin connection with. theaccompanying drawing, in which:

Fig. l is a perspective-view of. a wlimpj'diaphragm actuator embodyingthelfeatures of.-the presentinvention,

a portion of one of the endplates' oftlie actuator being the actuator;

Fig. 2 is a sectional view taken along the lines 2-2 of Fig. 1 andthrough the center line of the output shaft of the actuator; and

Fig. 3 is a diagrammatic illustration of a control system wherein theactuator of the present invention is employed.

Referring now to the drawing, and more particularly to Figs. 1 and 2thereof, the diaphragm actuator of the present invention is thereinillustrated as comprising an upper housing member indicated generally atand a lower housing member indicated generally at 11, the housing lfl'being provided with the side flanges 12 and 13 and the housing 11 beingprovided with the side flanges 14 and 15, these side flanges beingsecured together by means of the bolts 16. The housing 10 is alsoprovided with the end flanges 18 and 19 and the housing 11 is providedwith the end flanges 20 and 21 to which the end plates 22 and 23 aresecured by means of the bolts 24 so that a rectangular actuator unit isprovided. there is provided a bearing member 29 which slidably supportsthe output shaft 30 of the actuator, it being understood that a suitablepacking gland of high temperature material may be employed between theshaft 30 V 2,94s,ooo 7 g 45 and the supporting edges of the housing 10.In a similar manner, the variable area diaphragm 34 is supportedthroughout the length of the opposed flanges 53, 54 although the opposedends of the diaphragm 34 are completely unsupported between the member56 and the housing 11 so as to permit the diaphragm to form truecatenaries between the sloping surfaces 65 and 66 of the member 56 andthe sloping walls 67 and 68 of the lower housing 11. The ends of thepiston head 45 and the clamping members 51 and 56 are preferably spacedfrom the inner surfaces of the end plates 22 and 23 by about 0.010 inchto provide sufiicient clearance so that the ends of these members do notstrike the end plates 22, 23 throughout the stroke of the actuatorwhich, at the same time, provide adequate support for the clampedportions of the diaphragms 32 and 34.

In order to provide a very small gap, preferably in the order of 0.0001inch, between the unsupported end portions of the diaphragms 32 and 34and the inner surfaces of the end plates 22 and 23, the'ends of thehousings 10 and 11 are filled with a low melting point solder,

In the top wall 28 of the upper housing 10 and the bearing 29 to preventleakage around the shaft 30,

permitting the shaft to be moved easily, as will be readily understoodby those skilled in the art.

In the illustrated embodiment of the invention a pressure ratio typeactuator is provided wherein a first limp diaphragm 32, of constantarea, and a second limp dia- 1 In a similar manner, the opposed parallelsides 39 and 40 of the diaphragm 34 are clamped between the spacer'members 37, 38 and the side flanges 14 and 15 of the lower housingmember 11. p

A rectangular piston head is threaded onto the end of the output shaft30 of the actuator within the upper housing 10 and is secured thereto bymeans of the roll pin 46, the piston 45 being provided with the opposedparallel skirt portions 47 and 48. The intermediate portion 50 of theconstant area diaphragm 32 is clamped I against the bottom surface ofthe piston head 45 by means of a clamping member 51 which is secured tothe piston head 45 by means of the bolts 52, it being understood thatthe skirt portions 47, 48 of the piston 45 are spaced from the walls ofthe housing 10 by an amount suflicient to permit the diaphragm 32 toflex without crimping or producing a permanent bend in the diaphragmthroughout the stroke of the actuator.

The member 51 is provided with a pair of opposed, parellel, downwardlyextending flanges 53 and 54 which are adapted to receive therebetweenthe upstanding flange portion 55 of a second clamping member 56, themember 56 being of inverted Y-shaped cross section. The intermediateportion 58 of the variable area diaphragm 34 is positioned over theflange 55 and is clamped between theopposed flanges 53 and 54 by meansof the bolts 60, the openings 60a being provided through the flanges 53,54 and the diaphragm 34 to equalize pressure on both sides of theseflanges. It will thus be evident that the constant area diaphragm 32 issupported throughout the entire length of the piston head 45 althoughthe opposed ends of the diaphragm 32 are entirely unsupported in theareas between the piston head 45 and the walls of the housing 10 so thatthe diaphragm 32 assumes true catenaries between the supporting edges ofthe piston head with the end plates 22, 23' removed, so that the piston45, the members 51 and 56 and the diaphragms 32 and 34 are preventedfrom moving, relative to the housings 10 and 11. The entire exposed endportions of the actuator unit including the surfaces of the end flanges18, 20 and 19, 21, the ends of the members 51 and the ends of thediaphragms 32 and 34 are finished to a high degree of flatness by asuitable grinding operation followed by a suitable lapping operation.The inner surfaces of the end plates 22 and 23 are also subjected to asimilar grinding and lapping operation. Preferably, the diaphragms 32and 34, which are of thin sheet metal, are initially cut slightly largerthan the housings 10 and 11 so that the ends of these diaphragmsinitially extend beyond the end flanges 1 8, 20 and 19, 21. During theabove described grinding operation the cut edge of the diaphragms, whichmay be deformed during the cutting operation, are removed so that anextremely narrow gap between the diaphragms and the end plates may beachieved. After the end portions of the actuator have been finished to aclose tolerance in the manner described above, the solder is melted andremoved from the housings 10 and 11 so that the piston 45 and diaphragms32, 34 are thereafter free to move with respect to the housings 10 and11, and the end plates 22 and 23 are then bolted in position.Preferably, a solder which melts at about 165 F. is used so that thesolder can be removed by merely flushing out the housings 10 and 11 withboiling water.

When the end portions of the actuator unit are precision ground in themanner described above, the end portions of the diaphragm 32 and 34 arevery closely spaced to the end plates 22 and 23 so that an effectiveseal between these members is provided while permitting the diaphragmsto assume the desired catenary shape so that stresses on the diaphragmare minimized.

In order to prevent the housings 10 and 11 from moving relative to eachother during the end grinding and lapping process described above, theflanges, 12, 14 and 13, 15 are drilled to receive suitable dowel pinsand 71 which maintain the housings 10 and 11 in the desired registrationduring the grinding and lapping operations.

In the illustrated embodiment, air is admitted to the dhamber 75 betweenthe diaphragms 32 and 34 through a suitable inlet 76 which may bepositioned in the end plate 22. Air is also introduced from anothersource into the chamber 78 between the diaphragm 32 and the upper wall28 of the housing 10 through the inlet 79.

In considering the operation of the actuator of the present invention,reference may be had to Fig. 3 wherein the actuator is employed in acontrol system to produce a .control movement of the output shaft 30 inaccordance with the pressure ratio developed in a gas turbineover-temperature control system. Thus, comactuator unit.

H pressor discharge-air is supplied through the conduit 90, 1

the filter unit 91 and the conduit 76 to the chamber 75 between thediaphragms 32 and 34. The compresser discharge air is also suppliedthrough a restricting orifice 92, which may be 'eitherfixed orvariable,to provide a control pressure which is suppliedthrough theconduit 93 andthe conduit 79 to the chamber 78 within the This control pressure isalso connected to four paralleled temperature sensitive control units95,

I each of the control units 95 being provided with a bleed orifice whichvents the control pressure line 93 to the atmosphere within apredetermined high temperature control band Each of the high temperaturecontrol units 95 may be substantially identical to the correspondingcontrol units shown and described in detail in a copendingapplicationofRudolfBeck, Hans W. ,Kretsch and Robert W. Stewart, Serial No. 439,784,filed June 28, 19 54, and assigned to the same assignee as the presentinvention, and reference may be had to this copend:

ing application for a detailed description of a suitable temperaturecontrol unit 95., Movement of the output and assuming that thetemperature of the hot gases measured by the units 95 is below thetemperature control band, allof the control orifices in the units 95will be closed so that the'control pressure supplied over the conduits93and 79 to the control pressure chamber 78 will equal the pressure in thesupply chamber 75. When the pressures on both sides of the diaphragm 32are equalized the output shaft 30 is moved to its fully retractedposition wherein the end flanges 100 and 101 of the member 56 rest onthe bottom of the housing 11, the chamber 102 below the diaphragm 34being vented to atmosphere through the opening 103. As the gas streamtemperature increases, the control orifices of the temperature controlunits 95 open so that pressure in the control line 93 is vented toatmosphere and the control pressure in the chamber 78 is thereby reducedproportionately. Accordingly, the output shaft 36 is moved upwardlyuntil the effective area of the variable area diaphragm 34 becomessuificiently large to balance the pressures set up in the chambers 75,78 and 102. A further increase in temperature will result inproportional reduction of the control pressure in the chamber 78 andconsequent proportional extension of the output shaft 30 until the fulltemperature control range is travelled, at which time the piston head 45assumes the position shown in dotted lines in Fig. 2 wherein the skirtportions 47, 48 thereof rest against the upper wall 28 of the housingand the output shaft 30 is fully extended. It will thus be evident thatthe output shaft 30 of the pressure ratio actuator has a unique positionfor each value of the ratio between the supply pressure in the chamber75 and the control pressure in the chamber 78 throughout the temperaturecontrol band so that the output shaft 30 has a substantially linearstroke throughout the desired control band. It will also be noted thatthe ratio between the supply pressure and the control pressure is aunique function of the ratio between the size of the restrictor 92 andthe total effective orifice size of the four paralleled temperaturecontrol units 95.

With the above described arrangement, variations in the compressordischarge pressure supplied to the supply pressure chamber 75 do notproduce movement of the output shaft 30 so that the control systemfiunctions properly over the wide range of compressor dischargepressures which are experienced in actual jet aircraft operation. Thisis because the limp diaphragms 32 and 34 have substantially no springrate because the diphragms 32 and 34 are not stretched or distorted inany ,waybut, instead are merely flexed as theyroll on the opposedsurfaces of. the piston head and housings with the ends thereof incontiguity with the inner surfaces of the end plates. Preferably, theactuator unit is constructed as .an elongated unit with the distancealong the rolling edges of the diaphragms relatively large as comparedto the distance along the ends which are in contiguity with theendplates so that leakage is reduced to a minimum. In this connection itwill be understood that even ifthe ends of the diaphragms have ascraping or wiping engagement with the end plates, the friction thusproduced is const ant throughout the stroke of the actuator andwouldmerely result in a so-called dead band in the. action of the overallcontrol system. It will also be noted that the edges of the diaphragmsact as self-cleaning knife edges with no appreciable contact area underwhich dirt particles from the pneumatic supply can lodge. may beemployed in accordance with the present inven- .tion as a long strokeactuator having characteristics Accordingly, a relatively long, limpdiaphragm similar to a conventional piston and cylinder arrange- ,menttbut.with the additional advantages of low friction and littlesusceptibility .to dirt in the pneumatic supply.

In this connection, it will be understood that a conventignal piston 'with a long surface in contact with the cylinder walls can be easilyjammed by small dirt particles which may be caught between the pistonand the cylinder walls-whereas with the self-cleaning knife edge actionprovided by the present invention, such jamming and binding ofthe pistonare avoided. It will also be noted that if the diaphragms 32 and 34extend more than thqhousings ,10, 11, .due tothe hot gases supplied tothe chambefi75gthejedges ofthese diaphragms move closer we the surfacesof the end plates to provide a better sealing action so that less hotgases are brought into the chamber. This temperature compensating actiontends to prevent the diaphragm edges from being bent or jammed againstthe end plates.

While the limp diaphragm construction is particularly suitable for anactuator of the pressure ratio type for the reasons described in detailabove, it will be understood that the principles of the presentinvention may be employed in many forms of diaphragm actuated devices.Thus, for example, the constant area diaphragm 32 may be employed byitself either to replace a conventional piston and cylinder arrangementor as a pressure responsive control unit wherein the piston head isbiased to the desired control point by means of a calibrated spring oran evacuated bellows opposing the diaphragm, as will be readilyunderstood by those skilled in the art. On the other hand, if a greaterpressure ratio range is required the diaphragm 32 may be made a variablearea diaphragm by providing suitable sloping wall portions for thepiston head 45 and the upper housing 10.

While there has been described what is at present considered to be thepreferred embodiment of the invention, it will be understood thatvarious modifications may be made therein which are Within the truespirit and scope of the invention as defined in the appended claims.

What is claimed as new and is desired to be secured by Letters Patent ofthe United States is:

1. The method of making a pressure responsive actuator having a bodymember provided with side walls and end plates defining a rectangularopening therein, a piston mounted within said opening and a thinflexible diaphragm positioned within said opening and connected to saidpiston, said diaphragm having two opposed sides thereof supported onsaid body member adjacent said side walls, which comprises filling theends of said body member with a low melting point solder with said endplates disassembled to prevent relative movement of said diaphragm, saidbody member and said piston, finishing the exposed end portions of saidbody member and said diaphragm to a high degree of flatness, thereafterremoving said low melting point solder to permit movement of said pistonand diaphragm relative to said bodymember,

and thereafter assembling said end plates to said body a member withsaid end portions of said diaphragm in contiguity therewith. I

2. The method of making a pressure responsive actuator having a bodymember provided with side walls and end flanges which support end platesto define a rectangular opening therein, a piston mounted within saidopening, ing and connected to said piston, said diaphragm having twoopposed sides thereof supported on said body member adjacent said sidewalls, which comprises filling the ends of said body member with a lowmelting point solder with said end plates disassembled to preventrelative end plates defining a rectangular opening therein, a pistonmounted within said opening and a thin flexible diaphragm positionedwithin said opening and connected to said piston, said diaphragm havingtwo opposed sides thereof supported on said body member adjacent saidside walls, which comprises filling the ends of said body member with alow melting point solder with said end plates disassembled to preventrelative movement of said diaphragm, said body member and said piston,finishing the exposed end portions of said body member and saiddiaphragm to a high degree of flatness, finishing one surface of saidend plates to ahigh degree of flatness, removing said low melting pointsolder to permit movement of said piston and diaphragm relative tosaidbody member, and thereafter assembling said 'end plates to said bodymember with said end portions of said diaphragm in contiguity with saidfinished surfaces of said end plates.

4. The method of making a pressure responsive actuator havingcooperating housing members and removable end plates which define arectangular chamber, a piston movably mounted within said chamber and athin, flexible diaphragm connected to said piston and having two opposedsides thereof secured between said housing members, which comprisesfilling the end portions of said chamber with a low melting point solderwith said end plates removed to prevent movement of said piston anddiaphragm relative to said housing members, finishing the end portionsof said housing members and said diaphragm to a high degree of flatness,removing said low melting point solder to permit movement of said pistonand diaphragm relative to said housing members, and thereafterassembling said end plates to said housing members with said finishedend portions of said diaphragm in contiguity therewith.

References Cited in the file of this patent UNITED STATES PATENTS2,760,260 Melchior d Aug. 28, 1956 2,780,176 Holzworth Feb. 5, 1957FOREIGN PATENTS 475,661 Canada t July 31, 1951 UNITED STATES PATENTOFFICE CERTIFICATE OF CORRECTION Patent N00 2,948,060 August 9, 1960 vJoseph F. Engelberger It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionand that the said Letters Patent should read as corrected below.

Column 6, line 31, for "extend" read expandcoi'umn 7, line 8, after"said opening," insert and a thin flexible n diaphragm positioned withinsaid openline 20 for flangse read flanges Signed and sealed this 4th dayof April 19610 (SEAL) Attest: ERNEST W. SWIDER XXWXXX ARTHUR W. CROCKERAttestmg Officer A ting Commissioner of Patents

